Chemical exposure: the impact on infant brain development

There are more than 80,000 industrial chemicals in widespread use across the US. Around 3,000 of these chemicals are in products that we come into contact with every day, including clothing, carpets, toys, cleaning products and cosmetics. But is it safe to be so frequently exposed to these chemicals?

Past studies have associated chemical exposure with negative impacts on health. In 2012, Medical News Today reported on a study suggesting that routine exposure to toxic chemicals may increase the risk of breast cancer, although this link has never been confirmed.

However, there is one health issue as a result of chemical exposure that is now widely accepted in the medical world - its effect on child brain development.

In 1993, a report from the National Research Council titled Pesticides in the Diets of Infants and Children first suggested that children, specifically the developing fetus, are significantly more sensitive to the toxic effects of chemicals than adults.

Numerous studies have supported this discovery. Last year, Medical News Today reported on a study from the Royal College of Obstetricians and Gynaecologists in the UK, suggesting that pregnant women need to be aware of unintentional chemical exposure, as it may impact the health of their unborn baby.

But how exactly can chemical exposure affect a child's development?

Toxic substances interfere with the brain's natural functions

Harmful chemicals can be absorbed into our bodies through our skin, or we can ingest them through air, food and drinks.

The US Agency for Toxic Substances and Disease Registry (ATSDR) states that pregnant women, children and elderly individuals are more sensitive to chemical exposure.

There are approximately 3,000 chemicals in products that we come into contact with every day, such as cleaning products, toys, clothing and carpets.

According to a 2006 study from the Center on the Developing Child at Harvard University in Cambridge, MA, some toxic chemicals can interfere with the natural function of genes, proteins and other small molecules in the brain.

This interference can lead to the onset of neurodevelopmental disorders, such as autism, attention deficit hyperactivity disorder (ADHD), cerebral palsyand dyslexia.

The paper states that the immature brain is much more vulnerable to toxic exposure than the brain of an adult.

The mature brain has a barrier of cells that stops chemicals in the blood stream from entering brain tissue. But the developing fetus does not have this protective barrier, meaning it is more vulnerable to toxic substances.

There are a series of chemicals that have been associated with neurodevelopmental disorders. These include lead, mercury, fluoride, dichlorodiphenyltrichloroethane (DDT), manganese, chlorpyrifos (a pesticide) and tetrachloroethylene (a solvent).

Lead can interfere with important neurotransmitters in the brain, including dopamine, glutamate and acetycholine, while mercury can disrupt brain development by blocking enzymes that regulate brain function. It also stops cells from dividing, meaning there are fewer neurons and support cells produced in the brain.

Hidden toxicity of chemicals worrying

US organizations, including the Environmental Protection Agency (EPA) and the Food and Drug Administration (FDA), have imposed regulations on chemicals that have been linked to neurodevelopmental disorders in order to protect children's health.

But a recent study from the Harvard School of Public Health in Boston, MA, states that there are 214 chemicals that have been linked to human brain damage that have not been regulated.

Furthermore, the researchers note that of the 80,000 chemicals widely used in the US, the vast majority of these have not been tested for their toxic effects.

"Sadly, in the US, the legal requirements for testing chemicals before they come on to the market are almost non-existent," said study author Dr. Phillip Landrigan, of the Department of Preventive Medicine at the Icahn School of Medicine at Mount Sinai in New York, NY.

He told Medical News Today:

"These chemicals are put into products, they are not tested, they get out into the environment and get into people.

Some, I am quite sure, will turn out to be benign. But I am sure there are some that are hidden. There are some that are probably causing harm that we have not yet recognized as dangerous."

Recent studies have focused on the potential harm that certain unregulated chemicals can cause.

We recently reported on research suggesting that synthetic chemicals used in food packaging - known as food contact materials (FCMs) - may leak into the food we eat and harm our long-term health.

Other research has found that pregnant women exposed to phthalates - chemicals found in some deodorants, lotions and perfumes - may be at increased risk of preterm birth.

But according to the study researchers, "our very great concern is that children worldwide are being exposed to unrecognized toxic chemicals." They say this exposure could lead to a "global neurodevelopmental epidemic."

So what can be done to prevent this possible epidemic?

Change in US chemical policy needed

In a 2011 study, Dr. Landrigan and colleagues say "the finding that children are uniquely vulnerable to synthetic chemicals indicates the need for fundamental revision of US chemical policy."

Talking to Medical News Today, Dr. Landrigan said that US policymakers would benefit from adopting a chemical testing policy similar to that enacted by the European Union (EU) in 2007.

The Regulation on Registration, Evaluation, Authorisation and Restriction of Chemicals(REACH), states that the responsibility of chemical testing should lie with the chemical industry, not the government.

The chemical industry within the EU compiles data on the potential risks of commercial chemicals and sends this information to a central database of the European Chemical Agency in Helsinki, Finland. This data is then reviewed and presented to consumers and environmental professionals.

Dr. Landrigan said that this policy is beginning to make a difference to the levels of chemical exposure in the EU.

The EPA recently awarded $3 million to researchers studying how chemical exposure can impact brain development.

But there are some positive moves toward improved chemical testing in the US.

The EPA recently announced it has awarded more than $3 million to researchers studying how chemical exposure can affect brain development.

According to Lek Kadeli, of the EPA's Office of Research and Development:

"By better predicting whether chemicals have the potential to impact health and human development, these grants will not only advance the science necessary to improve chemical safety, but protect the wellbeing and futures of children in this nation."

Dr. Landrigan said research such as this is very valuable to the future of chemical testing.

"There is always need for more research. To carry out chemical testing you need to know what you are looking for, and it is the research that tells us what to look for," he explained.

The need for greater awareness of chemical exposure

Dr. Landrigan believes that awareness as to how chemical exposure impacts brain development has improved in the medical world over the past 10-15 years.

"I think 10 or 15 years ago, it wasn't widely appreciated how vulnerable a fetus is in the womb. The brain and other organ systems are still going through the most rapid and complex changes of their development," he told us.

However, he noted that awareness within the general public is an area that needs more focus, and health professionals can play a very important role in increasing awareness among populations that are vulnerable to chemical exposure.

He said:

"The three groups of doctors that really need to be aware of these issues are people that are OB/GYNs (obstetricians/gynecologists), pediatricians and family doctors - who are seeing both pregnant women and young children.

Most doctors now counsel women about not drinking alcohol during pregnancy, not smoking and making sure they get enough folic acid in their diet. Now they need to add environmental warnings to that."

Ways to reduce chemical exposure during pregnancy

According to the ATSDR, there are a number of ways that vulnerable individuals can reduce their risk of chemical exposure.

Women are advised to avoid painting during pregnancy, as many paints contain chemicals that can be absorbed through the skin.

Pregnant women are advised to avoid painting, as paint contains a variety of chemicals that can be absorbed through the skin.

Dr. Landrigan told us that both women and children should also be aware of moving into older properties that may be decorated with lead paint.

"We have a big problem in the US with lead paint, so I would advise people to be very careful if they are moving into a house or an apartment that was built before the mid-1970s. They should get it tested for leaded paint."

The use of pesticides should also be avoided during pregnancy. When gardening, pregnant women are advised to wear gloves to avoid potential contact with pesticides.

Dr. Landrigan noted that women should also take their diet into consideration when it comes to chemical exposure during pregnancy.

Although it is important that expectant mothers include fish in their diet, some fish may contain high levels of chemicals.

Dr. Landrigan explained:

"It is very important that pregnant women eat fish because the omega-3 fatty acids in fish are very good for infant brain development. But that said, women need to know that not all fish are equal. Some have higher levels of PCP (pentachlorophenol) and mercury while others do not."

The ATSDR state that fish lower in mercury include shrimp, trout, crab, calamari and wild Alaska salmon.

Furthermore, Dr. Landrigan said pregnant women should eat organic foods when they can afford to do so.

"Very big studies have shown that people who eat organic food have 90% lower levels of pesticide in their bodies than people who eat normal pesticide-treated food," he added.

The future of chemical exposure

These tips may help to reduce chemical exposure. However, given the number of everyday products that these substances are in, it may be impossible to completely eliminate exposure to potentially harmful toxins.

But with the EPA funding more research into how these chemicals impact brain development, changes to US chemical policy may be just around the corner.

As Dr. Landrigan and colleagues have previously stated:

"Creating a new chemical policy explicitly protective of health could prevent disease and dysfunction in childhood and across the lifespan, reduce health and education costs, increase national productivity, and promote better health and well-being for all Americans."

The ATSDR have published information on how to reduce exposure to chemicals.